Illuminating device, image reading apparatus including the illuminating device, and image forming apparatus including the image reading apparatus

ABSTRACT

An illuminating device capable of stably illuminating an irradiated object such as a document while suppressing light loss with a simply structure is provided. 
     An LED array and a reflective plate are disposed sandwiching a slit (St) through which light reflected by a document MS passes and a light-guiding member is disposed on the side of the LED array. The light-guiding member includes a direct emission unit disposed between an illumination range y centered on a document reading position and the LED array and an indirect emission unit disposed between the reflective plate and the LED array, a light incidence face of the direct emission unit and a light incidence face of the indirect emission unit are disposed at mutually different position around the LED array, and the LED array is disposed on a side of an interior angle formed by the light incidence faces.

This application is a continuation of co-pending application Ser. No.13/502,678 filed on Apr. 18, 2012, and for which priority is claimedunder 35 U.S.C. §120, application Ser. No. 13/502,678 is the nationalphase of PCT International Application No. PCT/JP2010/068150 filed onOct. 15, 2010 under 35 U.S.C. §371, which claims the benefit of priorityof JP2009-251251 filed Oct. 30, 2009. The entire contents of each of theabove-identified applications are hereby incorporated by reference.

TECHNICAL FIELD

The present invention relates to an illuminating device that illuminatesan irradiated object such as a document, an image reading apparatusincluding the illuminating device, and an image forming apparatusincluding the image reading apparatus.

BACKGROUND ART

Illuminating devices of this type are mounted on, for example, an imagereading apparatus to be used, and each include a plurality oflight-emitting elements (e.g., LEDs) that are arranged in a row andparallel to a main scanning direction for reading a document, andilluminate the document using these light-emitting elements. The imagereading apparatus reads the entire document by repeatedly scanning thedocument being illuminated by the illuminating device along the mainscanning direction, while scanning the document also in a sub-scanningdirection. The image of the read document is output to a printer or thelike to be recorded on a recording sheet.

In this illuminating device, although it is desirable to cause all thelight emitted from the light-emitting elements to enter the readingrange of the document, actually, it is not possible to cause all thelight to enter the reading range of the document, causing light loss,and thus reducing the light loss is desired.

For this reason, in Patent Document 1, a condensing body is provided inthe light emission direction of the light-emitting elements such thatalmost all the light from the light-emitting elements enters theincident-side lens of the condensing body to be emitted from thecondensing body toward the reading range of the document, or a prismface is formed in a part of the condensing body or a reflective plate isprovided separately from the condensing body such that light transmittedthrough the condensing body is reflected by the prism face or thereflective plate to be emitted toward the reading range of the document,thereby attempting to reduce the light loss.

Also, in Patent Documents 2 and 3, the light-emitting elements and alight-guiding body are mounted on a substrate, and the light-guidingbody is positioned on the light emission side of the light-emittingelements such that light from the light-emitting elements is condensedwith the light-guiding body to be emitted toward the reading range ofthe document, or such that light that has not passed through thelight-guiding body is reflected by the reflective plate to be emittedtoward the reading range of the document, thereby attempting to reducethe light loss.

PRIOR ART DOCUMENTS Patent Documents

-   [Patent Document 1] JP 2005-102112A-   [Patent Document 2] JP 2008-35036A-   [Patent Document 3] JP 2008-35043A

SUMMARY OF INVENTION Problems to be Solved by the Invention

However, Patent Document 1 discloses a configuration in which theincident-side lens of the condensing body is disposed near thelight-emitting elements such that light transmitted through thecondensing body is reflected by the prism face or the reflective plateto be emitted toward the document, and thus if the position of theincident-side lens of the condensing body is displaced even slightlywith respect to the light-emitting elements, the path of the lightpassing through the condensing body greatly deviates, which greatlyincreases the light loss. However, Patent Document 1 does not clearlydisclose a specific structure for supporting the condensing body andadjusting the position thereof, which indicates that realizing such astructure is difficult.

Also, although light that has not passed through the light-guiding bodyis reflected by the reflective plate to be emitted toward the documentin Patent Documents 2 and 3, since the light that has not passed throughthe light-guiding body is dispersed light, it is impossible to cause allthe light to enter the reflective plate, which results in insufficientreduction of the light loss.

In view of these problems of conventional techniques, it is an object ofthe present invention to provide an illuminating device capable ofstably illuminating an irradiated object such as a document whilesuppressing light loss with a simple structure, an image readingapparatus including the illuminating device, and an image formingapparatus including the image reading apparatus.

Means for Solving the Problems

In order to solve the foregoing problems, an illuminating device of thepresent invention is an illuminating device including: a light-emittingelement; a light-guiding member that guides light from thelight-emitting element toward an irradiated object; and a reflectivemember that reflects the light from the light-emitting element, theilluminating device illuminating the irradiated object with light thathas been transmitted through the light-guiding member and light that hasbeen transmitted through the light-guiding member and reflected by thereflective member, wherein the light-emitting element and the reflectivemember are disposed to sandwich a path through which light reflected bythe irradiated object passes, and the light-guiding member is disposedon a side of the light-emitting element, the light-guiding memberincludes a direct emission unit that is disposed between the irradiatedobject and the light-emitting element, and through which light emittingfrom the light-emitting element to the irradiated object is transmitted,and an indirect emission unit that is disposed between the reflectivemember and the light-emitting element, and through which light emittingfrom the light-emitting element to the irradiated object via thereflective member is transmitted, and a light incidence face of thedirect emission unit and a light incidence face of the indirect emissionunit are disposed at mutually different positions around thelight-emitting element, and the light-emitting element is disposed on aside of an interior angle formed by the light incidence faces.

With the illuminating device of the present invention, light emittedfrom the light-emitting element passes through one of a direct pathextending from the direct emission unit to the irradiated object or anindirect path extending from the indirect emission unit to theirradiated object via the reflective member, thereby illuminating theirradiated object. Since one of the paths, namely, the direct path, isshort, light incident on the irradiated object is scarcely dispersed,and thus it is possible to clearly illuminate the irradiated object withincident light reaching through the direct path, but the irradiatedobject is readily unevenly illuminated. Also, since the other path,namely, indirect path, is long, light incident on the irradiated objectis dispersed such that the level of illumination of the irradiatedobject with the light reaching through the indirect path is low.However, uneven illumination of the irradiated object rarely occurs. Bycombining illumination through the direct path with that through theindirect path, it is possible to stably illuminate the irradiated objectwhile suppressing the light loss.

Also, with the illuminating device of the present invention, an area ofthe light incidence face of the direct emission unit differs from anarea of the light incidence face of the indirect emission unit, or thearea of the light incidence face of the direct emission unit is largerthan the area of the light incidence face of the indirect emission unit.

By setting the area of the direct emission unit and the area of theindirect emission unit as described above, it is possible toappropriately set the ratio between the illumination level of theirradiated object through the direct emission unit and the illuminationlevel of the irradiated object through the indirect emission unit, thatis, light distribution between the direct path and the indirect path.Also, since the direct path and the indirect path have mutuallydifferent orientations relative to the reading range of the irradiatedobject, even if a shadow of an end portion of the irradiated object isgenerated due to the light emitting along one of the paths illuminatingthe end portion of the irradiated object, that shadow of the end portionof the irradiated object is illuminated by the light emitting along theother path, and thus it is possible to vanish the shadow of the endportion of the irradiated object.

Also, with the illuminating device of the present invention, a lightemission face of the light-emitting element faces a side of the indirectemission unit.

Also by setting the orientation of the light emission face of thelight-emitting element as described above, it is possible toappropriately set the ratio between the illumination level of theirradiated object through the direct emission unit and the illuminationlevel of the irradiated object through the indirect emission unit.

Further, with the illuminating device of the present invention, each ofthe light incidence face of the direct emission unit and the lightincidence face of the indirect emission unit is a flat surface.

In this case, even if the light-guiding member is displaced, a situationwill hardly occur in which the amount of incident light from thelight-emitting element on the direct emission unit and the amount ofincident light from the light-emitting element on the indirect emissionunit greatly drop at the same time, which suppresses the light loss.

Also, with the illuminating device of the present invention, each of thelight emission face of the direct emission unit and the light emissionface of the indirect emission unit has a convex shape and a condensingproperty.

With this configuration, it is possible to appropriately specify theillumination range of the irradiated object.

Further, with the illuminating device of the present invention, asubstrate on which the light-emitting element is mounted is provided,and the direct emission unit and the indirect emission unit cover asurface of the substrate on which the light-emitting element is mounted,or a substrate on which the light-emitting element is mounted isprovided, and at least one of the direct emission unit and the indirectemission unit is directly fixed to the substrate.

With this configuration, it is possible to easily position the directemission unit and the indirect emission unit with respect to thelight-emitting element, and thus the irradiated object can be stablyilluminated.

Further, with the illuminating device of the present invention, adirection of light reflected by the reflective member is oriented to aposition that is beyond a reading reference position of the irradiatedobject.

In this case, even in a state in which the irradiated object comes offthe reading reference position, it is possible to fully illuminate theportion of the irradiated object that comes off the reading referenceposition.

For example, the direction of reflected light is set with a part of areflection surface of the reflective member.

In this case, it is possible, with the light reflected by the reflectivemember, not only to illuminate a position beyond the reading referenceposition of the irradiated object, but also to illuminate otherposition, which can expand the range that can be illuminated by thelight reflected by the reflective member.

An image reading apparatus of the present invention includes theilluminating device of the present invention.

Also, an image forming apparatus of the present invention includes theimage reading apparatus of the present invention.

Also with the image reading apparatus and the image forming apparatus,the same effects as those of the above-described illuminating device ofthe present invention can be achieved.

Effects of the Invention

According to the present invention, light-emitting elements and areflective member are disposed such that the passing path of lightreflected by an irradiated object runs therebetween, and a light-guidingmember is provided on the light-emitting element side. The light-guidingmember includes a direct emission unit that is disposed between theirradiated object and the light-emitting elements, and that transmitslight from the light-emitting elements toward the irradiated object, andan indirect emission unit that is disposed between the reflective memberand the light-emitting elements, and that transmits light from thelight-emitting elements toward the irradiated object via the reflectivemember. A light incidence face of the direct emission unit and a lightincidence face of the indirect emission unit are disposed at mutuallydifferent positions around the light-emitting elements, and thelight-emitting elements are disposed on the side of an interior angleformed by the light incidence faces. Accordingly, light emitted from thelight-emitting elements emits along either a direct path extending fromthe direct emission unit to the irradiated object, or an indirect pathextending from the indirect emission unit to the irradiated object viathe reflective member, thereby illuminating the irradiated object.Although since one of the paths, namely, the direct path, is short,light incident on the irradiated object is scarcely dispersed such thatit is possible to illuminate the irradiated object clearly with theincident light reaching through the direct path, the irradiated objectis readily illuminated unevenly. Also, although since the other path,namely, the indirect path, is long, light incident on the irradiatedobject is dispersed such that the level of illumination by the lightreaching through the indirect path of the irradiated object is low,uneven illumination of the irradiated object rarely occurs. By combiningillumination through the direct path with that through the indirectpath, it is possible to stably illuminate the irradiated object whilesuppressing light loss.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a cross-sectional view showing an image forming apparatusincluding an image reading apparatus to which an illuminating deviceaccording to an embodiment of the present invention is applied.

FIG. 2 is an enlarged cross-sectional view of the image readingapparatus and a document transport apparatus in FIG. 1.

FIG. 3 is a cross-sectional view schematically showing a first scanningunit of the image reading apparatus.

FIG. 4 is a perspective view schematically showing the first scanningunit in FIG. 3.

FIG. 5 is a cross-sectional view showing a state of illumination by anilluminating device of the first scanning unit in FIG. 3.

FIG. 6A is a graph showing the light intensity for a first indirectpath, and FIG. 6B is a graph showing the light intensity for a secondindirect path.

FIG. 7 shows an illumination state of a book.

FIG. 8 shows an illumination state of a rear end portion of a document.

MODES FOR CARRYING OUT THE INVENTION

Embodiments of the present invention will be described below in detailwith reference to the attached drawings.

FIG. 1 is a cross-sectional view showing an image forming apparatusprovided with an image reading apparatus to which an illuminating deviceaccording to an embodiment of the present invention is applied. Theimage forming apparatus 100 is a so-called multifunction peripheralhaving a scanner function, a copy function, a printer function, afacsimile function, and the like. The image forming apparatus 100transmits an image of a document read by an image reading apparatus 41to the outside (this function corresponds to a scanner function), andforms and records on a recording sheet, in color or monochrome, an imageof the read document or an image received from the outside (thisfunction corresponds to a copy function, a printer function, and afacsimile function).

The image forming apparatus 100 includes a laser exposure apparatus 1,development apparatuses 2, photosensitive drums 3, charging units 5,cleaner apparatuses 4, an intermediate transfer belt apparatus 8, afixing apparatus 12, a paper transport path S, a paper feed tray 10, apaper discharge tray 15, and the like, in order to print an image on arecording sheet.

Image data processed in the image forming apparatus 100 corresponds to acolor image using colors consisting of black (K), cyan (C), magenta (M),and yellow (Y), or corresponds to a monochrome image using a monochromecolor (e.g., black). Accordingly, four each of the developmentapparatuses 2, the photosensitive drums 3, the charging units 5, and thecleaner apparatuses 4 are provided so as to form four types of tonerimages corresponding to the respective colors, and respectivelyassociated with black, cyan, magenta, and yellow to constitute fourimage stations Pa, Pb, Pc, and Pd are formed.

The photosensitive drums 3 each have a photosensitive layer on theirsurfaces. The charging units 5 are charging means for uniformly chargingthe surfaces of the photosensitive drums 3 to a predetermined potential.As the charging units 5, a contact-type charging unit using a roller orbrush, or a charger-type charging unit is used.

The laser exposure apparatus 1 is a laser scanning unit (LSU) providedwith laser diodes and reflecting mirrors, and causes the chargedsurfaces of the photosensitive drums 3 to be exposed to light accordingto image data to form electrostatic latent images corresponding to theimage data on the surfaces.

The development apparatuses 2 develop the electrostatic latent imagesformed on the surfaces of the respective photosensitive drums 3 usingtoners of the respective colors, and form toner images on the surfacesof the photosensitive drums 3. The cleaner apparatuses 4 remove andcollect toners remaining on the surfaces of the respectivephotosensitive drums 3 after development and image transfer.

The intermediate transfer belt apparatus 8 is disposed above thephotosensitive drums 3, and provided with an intermediate transfer belt7, an intermediate transfer belt-driving roller 21, an idler roller 22,four intermediate transfer rollers 6, and an intermediate transferbelt-cleaning apparatus 9.

The intermediate transfer belt 7 is obtained by forming a film having athickness of approximately 100 μm to 150 μM into an endless belt. Theintermediate transfer belt-driving roller 21, the intermediate transferrollers 6, the idler roller 22, and the like support the intermediatetransfer belt 7 in a stretched and tensioned manner, and rotate theintermediate transfer belt 7 around in the direction of arrow C.

The intermediate transfer rollers 6 are supported in a rotatable mannernear the intermediate transfer belt 7, and pressed via the intermediatetransfer belt 7 against the respective photosensitive drums 3.

The toner images on the surfaces of the photosensitive drums 3 aresequentially transferred and superimposed on the intermediate transferbelt 7, and a color toner image (a toner image containing theabove-described colors) is formed on the intermediate transfer belt 7.The toner images are transferred from the photosensitive drums 3 to theintermediate transfer belt 7, using the intermediate transfer rollers 6pressed against the back face of the intermediate transfer belt 7. Theintermediate transfer rollers 6 are rollers each including a base thatis made of a metal (e.g., stainless steel) shaft having a diameter of 8to 10 mm, with the surface of the shaft being covered by an electricallyconductive elastic material (e.g., ethylene-propylene-diene rubber(EPDM), polyurethane foam, etc.). In order to transfer the toner images,a high-voltage transfer bias (a high voltage of the opposite polarity(+) to the charge polarity (−) of the toner) is applied to theintermediate transfer rollers 6, and the electrically conductive elasticmaterial enables a high voltage to be uniformly applied to a recordingsheet.

In this manner, the toner images on the surfaces of the photosensitivedrums 3 are superimposed on the intermediate transfer belt 7, and form acolor toner image represented by the image data. This color toner imageis transported together with the intermediate transfer belt 7, andtransferred to a recording sheet at a nip region between theintermediate transfer belt 7 and a transfer roller 11 a of a secondarytransfer apparatus 11.

A voltage (a high voltage of the opposite polarity (+) to the chargepolarity (−) of the toner) for transferring the toner image containingthe above-described colors on the intermediate transfer belt 7 to therecording sheet is applied to the transfer roller 11 a of the secondarytransfer apparatus 11. Furthermore, in order to constantly maintain thenip region between the intermediate transfer belt 7 and the transferroller 11 a of the secondary transfer apparatus 11, one of the transferroller 11 a of the secondary transfer apparatus 11 and the intermediatetransfer belt-driving roller 21 is made of a hard material (metal,etc.), and the other is made of a soft material such as an elasticroller (elastic rubber roller, foamable resin roller, etc.).

The toner image on the intermediate transfer belt 7 may not becompletely transferred by the secondary transfer apparatus 11 to therecording sheet, and toner may remain on the intermediate transfer belt7. This residual toner causes toner color mixing in a subsequent step.Accordingly, residual toner is removed and collected by the intermediatetransfer belt-cleaning apparatus 9. The intermediate transferbelt-cleaning apparatus 9 includes, for example, a cleaning blade thatis in contact with the intermediate transfer belt 7 and removes theresidual toner as a cleaning member. The idler roller 22 supports theintermediate transfer belt 7 from the back face at a point where thecleaning blade is in contact with the intermediate transfer belt 7.

After the color toner image is transferred at the nip region between theintermediate transfer belt 7 and the transfer roller 11 a of thesecondary transfer apparatus 11, the recording sheet is transported tothe fixing apparatus 12. The fixing apparatus 12 is provided with a heatroller 31, a pressure roller 32, and the like, and the recording sheetis sandwiched between the heat roller 31 and the pressure roller 32 andtransported.

The heat roller 31 is controlled so as to be at a predetermined fixingtemperature based on detection output of a temperature detector (notshown), and performs thermal pressing on the recording sheet with thepressure roller 32 to melt, mix, and press the color toner imagetransferred to the recording sheet, thereby thermally fixing the colortoner image to the recording sheet.

Meanwhile, the paper feed tray 10 is a tray in which recording sheetsare stored. The paper feed tray 10 is disposed in the lower portion inthe image forming apparatus 100, and supplies the recording sheets inthe paper feed tray 10.

The image forming apparatus 100 includes an S-shaped paper transportpath S for transporting the recording sheet supplied from the paper feedtray 10 via the secondary transfer apparatus 11 and the fixing apparatus12 onto the paper discharge tray 15. Along the paper transport path S, apaper pickup roller 16, paper registration rollers 14, the fixingapparatus 12, transport rollers 13, paper discharge rollers 17, and thelike are arranged.

The paper pickup roller 16 is a draw-in roller that is disposed in anend portion of the paper feed tray 10 and that feeds recording sheetssheet by sheet from the paper feed tray 10 into the paper transport pathS. The transport rollers 13 are a plurality of pairs of small rollersfor promoting and assisting transportation of a recording sheet.

The paper registration rollers 14 temporarily stop a recording sheetthat has been transported, align the leading edge of the recordingsheet, and transport the recording sheet with good timing matched withthe rotation of the photosensitive drums 3 and the intermediate transferbelt 7 such that the color toner image on the intermediate transfer belt7 is transferred to the recording sheet at the nip region between theintermediate transfer belt 7 and the transfer roller 11 a of thesecondary transfer apparatus 11.

For example, based on detection output of a pre-registration detectionswitch (not shown), the paper registration rollers 14 transport therecording sheet such that the leading edge of the color toner image onthe intermediate transfer belt 7 matches the leading edge of the imageformation region of the recording sheet in the nip region between theintermediate transfer belt 7 and the transfer roller 11 a of thesecondary transfer apparatus 11.

Furthermore, after the color toner image is fixed at the fixingapparatus 12, the recording sheet passes through the fixing apparatus12, and is discharged facedown by the paper discharge rollers 17 ontothe paper discharge tray 15.

Furthermore, when performing printing not only on the front face of therecording sheet but also on the back face, the paper discharge rollers17 on the paper transport path S are stopped and then rotated in reverseduring transportation of the recording sheet by the paper dischargerollers 17, the recording sheet is passed through a reversing path Srwhere the front and the back of the recording sheet are reversed, andthen the recording sheet is guided to the paper registration rollers 14.Subsequently, as in the case of the front face of the recording sheet,an image is recorded and fixed to the back face of the recording sheet,and the recording sheet is discharged onto the paper discharge tray 15.

Next, the image reading apparatus 41 and a document-transportingapparatus 42 will be described in detail. FIG. 2 is an enlargedcross-sectional view showing the image reading apparatus 41 and thedocument-transporting apparatus 42.

An inner side of the document-transporting apparatus 42 is axiallysupported by a hinge (not shown) on an inner side of the image readingapparatus 41, and the document-transporting apparatus 42 is opened orclosed by lifting or lowering an outer side portion thereof. When thedocument-transporting apparatus 42 is opened, a platen glass 44 of theimage reading apparatus 41 is exposed, and a document is placed on theplaten glass 44.

The image reading apparatus 41 is provided with the platen glass 44, afirst scanning unit 45, a second scanning unit 46, an imaging lens 47, acharge coupled device (CCD) 48, and the like. The first scanning unit 45is provided with an illuminating device 51 and a first reflecting mirror52. While the first scanning unit 45 is moving at a constant speed V bya distance according to the document size in a sub-scanning direction Y,the document on the platen glass 44 is exposed by the illuminatingdevice 51 and the reflected light is reflected by the first reflectingmirror 52 and guided to the second scanning unit 46, and, thus, theimage on the document surface is scanned in the sub-scanning directionY. The second scanning unit 46 is provided with a second reflectingmirror 53 and a third reflecting mirror 54. While the second scanningunit 46 is moving following the first scanning unit 45 at a speed V/2,the reflected light from the document is reflected by the secondreflecting mirror 53 and the third reflecting mirror 54 and guided tothe imaging lens 47. The imaging lens 47 condenses the reflected lightfrom the document onto the CCD 48, and forms the image on the documentsurface on the CCD 48. The CCD 48 repeatedly scans the image on thedocument in the main-scanning direction, and outputs analog imagesignals for one main scanning line at each instance of scanning.

The first scanning unit 45 and the second scanning unit 46 respectivelyinclude pulleys (not shown). A wire (not shown) is wound onto thesepulleys, the wire is driven by a stepping motor, and, thus, the firstscanning unit 45 and the second scanning unit 46 are moved insynchronization.

Furthermore, the image reading apparatus 41 can read not only a stilldocument but also an image on the surface of a document that is beingtransported by the document-transporting apparatus 42. In this case, asshown in FIG. 2, the first scanning unit 45 is moved to a reading rangebelow a document-reading glass 65, and the second scanning unit 46 ispositioned according to the position of the first scanning unit 45.Then, in this state, the document-transporting apparatus 42 startstransportation of the document.

In the document-transporting apparatus 42, a pickup roller 55 is pressedagainst a document on a document tray 56 and rotated, the document isdrawn in and transported, the leading edge of the document is abuttedagainst registration rollers 62 for alignment, and, then, the documentis passed through between the document-reading glass 65 and a readingguide plate 66 and discharged from paper discharge rollers 58 onto apaper discharge tray 49.

While the document is being transported, the illuminating device 51 ofthe first scanning unit 45 illuminates the document surface via thedocument-reading glass 65, the reflected light from the document surfaceis guided by the reflecting mirrors of the first scanning unit 45 andthe second scanning unit 46 to the imaging lens 47, and condensed by theimaging lens 47 onto the CCD 48, the image on the document surface isformed on the CCD 48, and, thus, the image on the document surface isread.

Furthermore, when reading the back face of the document, an intermediatetray 67 has been rotated about a shaft 67 a as indicated by the dottedline, and the paper discharge rollers 58 are stopped during discharge ofthe document from the paper discharge rollers 58 onto the paperdischarge tray 49 such that the document is received by the intermediatetray 67. Then, the paper discharge rollers 58 are rotated in reverse,and the document is guided via a reverse transport path 68 to theregistration rollers 62, thereby reversing the front and the back of thedocument. Then, as in the case of the image on the front face of thedocument, the image on the back face of the document is read, theintermediate tray 67 is returned to its original position indicated bythe solid line, and the document is discharged from the paper dischargerollers 58 onto the paper discharge tray 49.

In this manner, the image on the document surface thus read by the CCD48 is output from the CCD 48 as analog image signals, and these analogimage signals are A/D converted into digital image signals. Thesedigital image signals are subjected to various types of image processingand then transmitted to the laser exposure apparatus 1 of the imageforming apparatus 100, the image is recorded on a recording sheet in theimage forming apparatus 100, and this recording sheet is output as aphotocopied document.

The document on the platen glass 44 or the document-reading glass 65 isilluminated by the illuminating device 51 of the first scanning unit 45.Here, it is desirable to reduce the light loss by causing almost all thelight emitted from an LED array 71 of the illuminating device 51 toenter the document.

Thus, the illuminating device 51 of this embodiment includes alight-guiding member 72 that directly guides the light emitted from theLED array 71 toward the document and guides the light toward areflective plate 73, and the reflective plate 73 that reflects the lightguided thereto by the light-guiding member 72 toward the document.Accordingly, almost all the light emitted from the LED array 71 iscaused to enter the document, thereby reducing the light loss.

Next, the configuration of the illuminating device 51 of this embodimentwill be described in detail. FIG. 3 is a cross-sectional viewschematically showing the first scanning unit 45. FIG. 4 is aperspective view schematically showing the first scanning unit 45.

As clearly seen in FIGS. 3 and 4, the first scanning unit 45 is providedwith the illuminating device 51, the first reflecting mirror 52, and amoving frame 74. The illuminating device 51 and the first reflectingmirror 52 are mounted on the moving frame 74, both ends of the movingframe 74 are slidably supported, and the moving frame 74 is moved in thesub-scanning direction Y by the pulley, the wire, and the steppingmotor.

The illuminating device 51 includes a substrate 75, the LED array 71mounted on the substrate 75, the light-guiding member 72 fixedlysupported by the substrate 75, and the reflective plate 73. Each ofthese substrate 75, LED array 71, light-guiding member 72 and reflectiveplate 73 is disposed such that the longitudinal direction thereof is ina main scanning direction X for reading a document MS, and hassubstantially the same length as the reading range in the main scanningdirection X.

The LED array 71 is made up of a plurality of LEDs 76 arranged in a rowin the main scanning direction X on the substrate 75. Each LED 76 isconnected to the wiring pattern of the substrate 75, and the wiringpattern of the substrate 75 is connected to a driver circuit (not shown)mounted on the moving frame 74 through a harness (not shown). The drivercircuit supplies power to the LEDs 76 through the harness and the wiringpattern of the substrate 75, thereby lighting on and off the LEDs 76.

The light-guiding member 72 is made of glass or synthetic resin havingtranslucency, and includes a direct emission unit 77 disposed between anillumination range y centered on the document reading position in thesub-scanning direction Y and the LED array 71, and an indirect emissionunit 78 disposed between the reflective plate 73 and the LED array 71.The direct emission unit 77 and the indirect emission unit 78 areconnected to each other so as to form a single unit, and the surfaceside of the substrate 75 is covered by these emission units 77 and 78.The direct emission unit 77 covers a portion obliquely above thesubstrate 75, that is, a portion on the side of the illumination range yin the sub-scanning direction Y, and the indirect emission unit 78covers a portion on the left of the substrate 75, that is, a portion onthe side of the reflective plate 73.

The indirect emission unit 78 includes a step unit 78 a on its innerside, and the step unit 78 a is fitted to an end of the substrate 75such that the indirect emission unit 78 is fixedly supported by thesubstrate 75. Also, the left end side of the direct emission unit 77 isconnected to the indirect emission unit 78, a right end 77 a of thedirect emission unit 77 is disposed on a projection 79 on the substrate75 and fixed, and the direct emission unit 77 is thereby fixedlysupported by the substrate 75.

The inner surfaces of the direct emission unit 77 and the indirectemission unit 78 (light incidence faces facing the LED array 71) areflat surfaces. The light incidence faces of the direct emission uniô 77

and the indirect emission unit 78 are disposed at mutually differentpositions around the LED Array 71, and the LED array 71

is disposed on the side of

an interior angle formed by these light incidence faces. Here, theinterior angle formed by the light incidence faces is an angle smallerthan 0180 degrees.

In addition, the outer surfaces of the direãt emission unit 77 and theindirect emission unit 78 (light emission faces facing the illuminationrange y in the sub-scanning direction Y and the reflective plate 73) areconvex. The outer convex surfaces of the emission units 77 and w8 areformed to condense light that has been transmitted through the emissionunit 77 and Light that has been transmitted through the emission unit 78and reflected by the reflective plate 73 onto the illumination range yin the sub-scanning direction Y.

Also, the space between the LED array 71 and the reflective plate 73 isformed as a slit St that extends in the main scanning direction X, andthe illumination range y in the sub-scanning direction Y is provideddirectly above the slit St, and the first reflecting mirror 52 ispositioned directly below the slit St. The light-guiding member 72 isdisposed on the LED array 71 side with respect to the slit St.

Light emission faces 76 a of the LEDs 76 of the LED array 71 face thereflective plate 73 side, and the optical axes of the LEDs 76 areoriented leftward. The emission range of the light from each LED 76 is arange that is centered on the optical axis of the LED 76 and covers, inany direction, up to approximately 90 degrees from the optical axis.Also, the color of the surface of the substrate 75 is white, and lightemitted from the LEDs 76 is reflected by the surface of the substrate75. Therefore, almost all the light from the LEDs 76 is emitted to a90-degree range α, which is a range between the surface of the substrate75 and an orthogonal plane that is orthogonal to the surface of thesubstrate 75 and passes through the LEDs 76.

In addition, the reflective plate 73 includes a first reflective face 73a and a second reflective face 73 b. The first and second reflectivefaces 73 a and 73 b are disposed tilted upward so as to be capable ofreflecting light emitted from the LED array 71 toward the illuminationrange y in the sub-scanning direction Y. Also, the second reflectiveface 73 b is slightly bent with respect to the first reflective face 73a to change the orientation of the second reflective face 73 b.

Furthermore, the first reflecting mirror 52 is disposed parallel to themain scanning direction and also tilted by 45 degrees with respect tothe scanning face (the surface of the platen glass 44 and the documentreading glass 65).

In the illuminating device 51 configured as described above, as shown inFIG. 5, when the LED array 71 on the substrate 75 emits light, the lightemitted from the LED array 71 enters the light incidence face of thedirect emission unit 77 of the light-guiding member 72, is transmittedthrough the direct emission unit 77, is condensed by the outer convexsurface of the direct emission unit 77, and enters the illuminationrange y in the sub-scanning direction Y on the surface of the platenglass 44 and the document reading glass 65 (document reading referenceposition).

When a light path from the LED array 71 to the illumination range y inthe sub-scanning direction Y via the direct emission unit 77 is a directpath D, the direct path D represents shortest linear paths from the LEDarray 71 to within the illumination range y, and the illumination rangey in the sub-scanning direction Y is illuminated by the light reachingthrough the direct path D.

Also, light emitted from the LED array 71 enters the light incidenceface of the indirect emission unit 78 of the light-guiding member 72, istransmitted through the indirect emission unit 78, is condensed by theouter convex surface of the indirect emission unit 78, enters the firstreflective face 73 a of the reflective plate 73 to be reflected by thefirst reflective face 73 a, and enters the illumination range y in thesub-scanning direction Y.

When a light path from the LED array 71 to the illumination range y inthe sub-scanning direction Y via the indirect emission unit 78 and thefirst reflective face 73 a is a first indirect path da, the firstindirect path da represents paths that are longer than the direct path Das a result of being bent at the first reflective face 73 a. Theillumination range y in the sub-scanning direction Y is illuminated alsoby the light reaching through the first indirect path da.

Furthermore, light emitted from the LED array 71 is transmitted throughthe indirect emission unit 78 of the light-guiding member 72, iscondensed by the outer convex surface of the indirect emission unit 78,enters the second reflective face 73 b of the reflective plate 73 to bereflected by the second reflective face 73 b, and enters an illuminationrange ys in the sub-scanning direction Y, the illumination range ysbeing 5 mm above the surface of the platen glass 44 and the documentreading glass 65 (document reading reference position).

When the light path from the LED array 71 to the illumination range ysin the sub-scanning direction Y via the indirect emission unit 78 andthe second reflective face 73 b is a second indirect path db, the secondindirect path db also represents paths that are longer than the directpath D as a result of being bent at the second reflective face 73 b. Thelight reaching through the second indirect path db illuminates theillumination range ys in the sub-scanning direction Y, which is 5 mmabove the document reading reference position. The illumination range ysat the position 5 mm above the document reading reference position isset by slightly bending the second reflective face 73 b with respect tothe first reflective face 73 a, as described above.

FIG. 6A is a graph showing the light intensity for the first indirectpath da, and FIG. 6B is a graph showing the light intensity for thesecond indirect path db.

Light emitting along the first indirect path da is condensed by theconvex surface of the indirect emission unit 78. Therefore, the lightintensity is high at the position corresponding to the surface of thedocument MS (document reading reference position), as shown in FIG. 6A,and is kept at a substantially constant level within the illuminationrange y in the sub-scanning direction Y at this surface position. Theillumination range y has a width of 3 mm extending from the center ofthe range y (reading position) both forward and backward in thesub-scanning direction Y, totally, a width of 6 mm.

Light emitting along the second indirect path db is condensed by theconvex surface of the indirect emission unit 78. Therefore, the lightintensity is high at the position 5 mm above the surface of the documentMS as shown in FIG. 6B, and is kept at a substantially constant levelwithin the illumination range ys in the sub-scanning direction Y at theposition 5 mm above the surface of the document MS. The illuminationrange ys is narrower than the illumination range y.

Accordingly, the illumination range y in the sub-scanning direction Y atthe same level as the surface of the document MS is illuminated by lightemitting along linear direct paths D, which are formed by the lightbeing transmitted through the direct emission unit 77, and also by lightemitting along first indirect paths da, which are formed by the lightbeing transmitted through the indirect emission unit 78 and reflected bythe first reflective face 73 a of the reflective plate 73. As a result,the surface of the document MS is evenly illuminated with strong light.

Also, the illumination range ys in the sub-scanning direction Y at theposition 5 mm above the surface of the document MS is illuminated withlight emitting along the second indirect paths db, which are formed bythe light being transmitted through the indirect emission unit 78 andreflected by the second reflective face 73 b of the reflective plate 73.Therefore, even if the surface of the document MS comes off the platenglass 44 or the document reading glass 65, the surface is illuminated.For example, in the state where a book is opened and placed on theplaten glass 44 as shown in FIG. 7, although the pages come off thesurface in a portion MS1 where the book is bound, the light emittingalong the second indirect paths db reaches and illuminates the portionof the pages coming off the surface as well.

Light emitted from the LED array 71 in this manner irradiates thedocument MS on the platen glass 44 or the document reading glass 65 viathe light-guiding member 72 or the reflective plate 73. Light reflectedby the document MS passes through the slit St (passing path of light),is reflected by the first reflecting mirror 52 such that the reflectedlight is emitted toward the second reflecting mirror 53 of the secondscanning unit 46 through an opening in a side wall of the moving frame74.

Incidentally, since the direct emission unit 77 condenses the lightincident on the inner flat surface of the direct emission unit 77 tocause the light to enter the illumination range y in the sub-scanningdirection Y, the larger the area of the inner flat surface of the directemission unit 77, the larger the amount of light that enters theillumination range y in the sub-scanning direction Y from the directemission unit 77.

Similarly, since the indirect emission unit 78 condenses the lightincident on the inner flat surface of the indirect emission unit 78 tocause the light to enter the illumination range y in the sub-scanningdirection Y, the larger the area of the inner flat surface of theindirect emission unit 78, the larger the amount of light that entersthe illumination range y in the sub-scanning direction Y from theindirect emission unit 78.

Accordingly, by appropriately setting the areas of the inner flatsurfaces of the direct emission unit 77 and the indirect emission unit78, it is possible to adjust a proportion between the amount of lightthat has been transmitted through the direct emission unit 77 and entersthe illumination range y in the sub-scanning direction Y and the amountof light that has been transmitted through the indirect emission unit78, reflected by the first reflective face 73 a of the reflective plate73, and enters the illumination range y in the sub-scanning direction Y.

Specifically, since a light emission face 76 a of the LED array 71 facesthe reflective plate 73 side, the amount of light emitted from the LEDarray 71 is large in the direction of the reflective plate 73. However,by setting the area of the indirect emission unit 78 interposed betweenthe LED array 71 and the reflective plate 73 to be smaller than the areaof the direct emission unit 77, it is possible to set the ratio betweenthe amount of light that enters the illumination range y via theindirect emission unit 78 and the first reflective face 73 a of thereflective plate 73 and the amount of light that enters the illuminationrange y via the direct emission unit 77 to, for example, 4:6 to 5:5.

Also, since light that has been transmitted through the direct emissionunit 77 and enters the illumination range y is condensed by the directemission unit 77 and also emits along a substantially linear and shortdirect path D, the level of illumination by the light is high. However,uneven illumination readily occurs due to the LEDs 76 of the LED array71 disposed separate from each other.

In contrast, although light that has been transmitted through theindirect emission unit 78, reflected by the first reflective face 73 aof the reflective plate 73, and enters the illumination range y iscondensed by the indirect emission unit 78, since the light emits alonga long and bent first indirect path da, it results in relativelydispersed light compared with the light transmitted through the directemission unit 77, and thus the light causes little uneven illuminationin spite of its low illumination level.

Therefore, it is possible to adjust the illumination level and unevenillumination by appropriately setting the areas of the direct emissionunit 77 and the indirect emission unit 78 so as to adjust the ratiobetween the amount of light that has been transmitted through the directemission unit 77 and enters the illumination range y and the amount oflight that has been transmitted through the indirect emission unit 78,reflected by the first reflective face 73 a of the reflective plate 73,and enters the illumination range y.

Also, the incident direction of light that has been transmitted throughthe direct emission unit 77 and enters the illumination range y differsfrom that of light that has been reflected by the reflective plate 73and enters the illumination range y. For this reason, even in the statewhere, as shown in FIG. 8 for example, a rear end portion m of thedocument MS is within the illumination range y, and light reflected bythe first reflective face 73 a of the reflective plate 73 enters therear end portion m of the document MS to generate a shadow of the rearend portion m, that shadow disappears due to entering of light that hasbeen transmitted through the direct emission unit 77. That is, since therear end portion m of the document MS is irradiated with light reachingfrom its front and back, the shadow of the rear end portion m of thedocument MS does not appear, and thus no shadow appears in the documentimage read by the CCD 48. In order to achieve this, it is preferable toset the ratio between the amount of light emitted to the illuminationrange y via the indirect emission unit 78 and the first reflective face73 a of the reflective plate 73 and the amount of light emitted to theillumination range y via the direct emission unit 77 to approximately4:6.

Furthermore, the inner flat surface of the direct emission unit 77 andthe inner flat surface of the indirect emission unit 78 face the LEDs 76of the LED array 71 in mutually different directions. Therefore, even ifthe light-guiding member 72 is displaced, a situation will hardly occurin which the amount of incident light from the LED array 71 to thedirect emission unit 77 and the amount of incident light from the LEDarray 71 to the indirect emission unit 78 greatly drop at the same time,which suppresses the light loss. In contrast, in Patent Document 1,since it has a configuration in which the incident-side lens of thecondensing body is disposed near the light-emitting elements, and lightthat has been transmitted through the condensing body is reflected bythe prism face or the reflective plate to be emitted toward thedocument, if the incident-side lens of the condensing body is displaced,even slightly, with respect to the light-emitting elements, the path oflight passing through the condensing body greatly deviates, whichgreatly increases the light loss.

Also, as shown in FIGS. 3 and 4, since the direct emission unit 77covers a portion obliquely above the LED array 71, and the indirectemission unit 78 covers a portion on the left of the LED array 71,almost all the light emitted from the LED array 71 within the 90-degreerange a is transmitted through the direct emission unit 77 or theindirect emission unit 78 to enter the illumination range y, whichsuppresses the light loss.

Also, since the color of the surface of the substrate 75 is white, lightreflected by the surface of the substrate 75 is also transmitted throughthe direct emission unit 77 or the indirect emission unit 78 to enterthe illumination range y, which suppresses the light loss.

Furthermore, since both the direct emission unit 77 and the indirectemission unit 78 are securely supported by the substrate 75 on which theLED array 71 is mounted, the direct emission unit 77 and the indirectemission unit 78 can be positioned with respect to the LED array 71 withhigh accuracy, and also positional displacement thereof hardly occurs,which can prevent the light loss due to the positional displacement.

Above, a preferred embodiment of the present invention was describedwith reference to the attached drawings, but of course the invention isnot limited to that embodiment. It will be clear to those skilled in theart that within the category described in the claims, various modifiedor revised examples can be arrived at, and it is understood that suchchanges or modifications also obviously fall within the technical scopeof the present invention. For example, the direct emission unit 77 andthe indirect emission unit 78 of the light-guiding member 72 may beformed as separate units.

DESCRIPTION OF REFERENCE NUMERALS

-   -   1 Laser exposure apparatus    -   2 Development apparatuses    -   3 Photosensitive drums    -   4 Cleaner apparatuses    -   5 Charging units    -   8 Intermediate transfer belt apparatus    -   10 Paper feed tray    -   11 Secondary transfer apparatus    -   12 Fixing apparatus    -   41 Image reading apparatus    -   42 Document transport apparatus    -   44 Platen glass    -   45 First scanning unit    -   46 Second scanning unit    -   47 Imaging lens    -   48 CCD (Charge Coupled Device)    -   51 Illuminating device    -   52 First reflecting mirror    -   53 Second reflecting mirror    -   54 Third reflecting mirror    -   65 Document reading glass    -   71 LED array    -   72 Light-guiding member    -   73 Reflective plate    -   74 Moving frame    -   75 Substrate    -   76 LEDs    -   77 Direct emission unit    -   78 Indirect emission unit    -   100 Image forming apparatus

The invention claimed is:
 1. An illuminating device comprising: alight-emitting element; a substrate on which the light emitting elementis mounted; a reflective member; and a light-guiding member that guideslight emitted from the light-emitting element toward an irradiatedobject and the reflective member, the illuminating device illuminatingthe irradiated object with light that has been emitted from thelight-emitting element and guided to the irradiated object by thelight-guiding member and with light that has been emitted from thelight-emitting element, guided by the light-guiding member and reflectedto the irradiated object by the reflective member, wherein thelight-emitting element and the reflective member are disposed tosandwich a path through which light reflected by the irradiated objectpasses, and the light-guiding member is disposed on a side of thelight-emitting element relative to the path, the light-guiding memberincludes a direct emission portion that is disposed between theirradiated object and the light-emitting element, and through whichlight emitted from the light-emitting element to the irradiated objectis transmitted, and an indirect emission portion that is disposedbetween the reflective member and the light-emitting element, andthrough which light emitted from the light-emitting element to theirradiated object via the reflective member is transmitted, thesubstrate comprises a white portion on a surface of the substrate, andthe white portion is provided at least between the light-emittingelement and the reflective member, and reflects the light emitted fromthe light-emitting element.
 2. The illuminating device according toclaim 1, wherein the white portion is provided between the light-guidingmember and the substrate.
 3. The illuminating device according to claim1, wherein the white portion reflects the light emitted from thelight-emitting element toward the light-guiding member.
 4. Theilluminating device according to claim 1, wherein a light-emittingelement emits light from a face of the light-emitting element, the facebeing perpendicular to the surface of the substrate.
 5. The illuminatingdevice according to claim 1, wherein the direct emission portion and theindirect emission portion are connected to each other.
 6. Theilluminating device according to claim 1, wherein a light emission faceof the light-emitting element faces a side of the indirect emissionportion.
 7. The illuminating device according to claim 1, wherein eachof the light emission face of the direct emission portion and the lightemission face of the indirect emission portion has a convex shape and acondensing property.
 8. An image reading apparatus comprising theilluminating device according to claim
 1. 9. An image forming apparatuscomprising the image reading apparatus according to claim 8.